<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
   *{
    padding: 0;
    margin: 0;
   }
   li{
    list-style-type:none;
    width: 100px;
    height: 40px;
    background: darkcyan;
    margin-right: 10px;
    float: left;
   }
   /* div{
    clear: both;
   } */
   /* ul{ */
    /* height: 40px; */
   /* } */
   ul::after{
    content: '';
    display: block;
    clear: both;
   }
  </style>
</head>
<body>
  <ul>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <!-- <div></div> -->
  </ul>
  <p>hello</p>
</body>
</html>